Portable electronic devices require high-performance miniaturised electronic components, preferably produced at low cost. In most line-powered applications, alternating current (AC) line filters are used to filter AC lines to direct current (DC) signals, making filtering capacitors a key necessity in modern electronic devices. Currently, aluminium electrolytic capacitors (AECs) are commonly used, which are bulky and have narrow electrochemical performance. Thus, replacing AECs with a compact capacitor design is highly desirable for future portable electronic devices but simultaneously very demanding. Here, we report the fabrication of an electrochemical capacitor with an electrode based on vertically aligned carbon nanostructures produced by a green plasma-enabled deposition technique. These capacitors delivered a high capacity of 1145 μF with a phase angle close to −80° at 100 Hz in a lab-scale two-electrode set-up. A prismatic prototype capacitor fabricated by stacking 10 pairs of electrodes (2.5 × 3.5 cm2) showed one of the lowest equivalent series resistance values, about 5.8 mΩ, with a high capacitance of ∼12 mF at 100 Hz. This performance delivered at the lab scale and in industrial-relevant environments suggests such electrochemical capacitors represent a suitable alternative to conventional AECs for high-frequency filtering applications. [Display omitted] • Eco-friendly plasma-designed vertical carbon nanostructures as binder-free electrodes. • Supercapacitor with excellent high-frequency capacitive response and line-filtering properties. • Design of a prototype with an ultra-high capacitance value of 12 mF at 100 Hz. • A facile supercapacitor design opens future directions to replace conventional filtering devices. [ABSTRACT FROM AUTHOR]